利用蒙地卡羅模擬在應變矽晶面上不同通道方向之電洞傳輸特性

Abstract

本篇論文主要著重於利用蒙地卡羅模擬在應變矽晶面上之電洞傳輸特性。目前，利用由製程所造成的單軸應力(uniaxial stress)來改善元件效能已經被廣泛地使用。在第一章中，將簡單的介紹外加應力於P型及N型通道金氧半場效電晶體的應用。在第二章中，介紹一種用來計算矽價電帶結構的鍵結軌域模型(bond orbital model)，其因為具有較可靠的高能量價電帶結構，可以利用來模擬快閃式記憶元件操作在高壓下的之熱載子行為。 第三章中，為了要考慮外加應力對價電帶結構的影響，又介紹了另一種計算價電帶結構的方法，Luttenger-Kohn模型，這方法也是主要利用來探討矽和應變矽的電洞傳輸特性。在第四章中，根據前兩章所得到的價電帶結構，使用蒙地卡羅(Monte Carlo)方法來模擬電洞的傳輸，其兩種模型對電洞傳輸特性的影響可以由模擬結果得知。此外，並在不同通道方向及加上不同應力大小的情況下，探討電洞傳輸特性的變化。而模擬結果顯示，外加單軸壓縮應力時，會對電洞的遷移率有所提升。最後在第五章對本論文做個總結。

This thesis will focus on the hole transport properties of bulk strained silicon by using a Monte Carlo simulation. For today’s technology, uniaxial–process induced stress is used to improve device performance. In chapter 1, the applications of uniaxial strain in pMOSFET and nMOSFET are described. The embedded silicon-germanium source and drain with uniaxial compressive strain is applied to pMOSFETs, while the contact etch stop layer with uniaxial tensile strain and strain memory technology (SMT) are used for nMOSFETs. In chapter 2, the valence band structures in bulk silicon are calculated by using a bond orbital model, which is appropriate for a high energy portion of valence band structures. This model can be used for hot carrier simulation in flash memory devices during channel hot electron (CHE) program. In chapter 3, another valence band structure calculation method, Luttinger-Kohn model, is used to take into account the strain effects and mainly focus on the mobility calculation. The simulation results also demonstrate the hole transport properties in unstrained and strained bulk silicon material, which will be shown in the next chapter. In chapter 4, a Monte Carlo method including a realistic valence band structure is developed to simulate hole transport properties. The differences of the transport properties calculated from the above two models are also shown. The channel orientation effect and strain effect on hole drift velocity and mobility are also evaluated. Our simulation results show that the hole mobility enhancement can be obtained with uniaxial compressive strain. Conclusions are finally given in chapter 5.